Experimental and theoretical characterization of molecular complexes formed between OCS and XY molecules (X, Y = F, Cl and Br) and their role in photochemical matrix reactions

Abstract

Molecular complexes between OCS and ClF, Cl₂, Br₂, or BrCl have for the first time been isolated in solid matrixes at low temperature, and characterized by their IR spectra. 1 : 1 adducts between OCS and ClF, Cl₂, or BrCl were formed by broad-band UV-visible photolysis of matrix-isolated FC(O)SCl, ClC(O)SCl or BrC(O)SCl, respectively. Co-deposition of gaseous mixtures of OCS and ClF or Br₂ diluted with Ar on a CsI window cooled to approximately 15 K led to the identification of 1 : 1 complexes, while similar mixtures of OCS and Cl₂ gave rise mainly to 1 : 2 species. The differences in the structures and stoichiometries of the molecular complexes may well be responsible for the different reaction channels observed for the photochemical matrix reactions between OCS and Cl₂ or Br₂. The structures, energy differences, vibrational spectra, and bonding properties of all the possible complexes formed between OCS and XY (XY = ClF, Cl₂, Br₂, or BrCl) have been studied with different theoretical approximations.